Besides excellent optical characteristics, polycarbonates (PC) have low equilibrium water absorption and excellent mechanical characteristics such as heat resistance, dimensional stability and impact strength, and thus are used as materials for molding an optical part such as a light guide plate, an optical substrate material, a lens and fiber. For example, high quality PC is required for an optical information recording medium in terms of less stamper fouling upon fabricating a substrate, improvement of transferability, durability of the recording film, long-term reliability of the PC substrate itself and else. In response to such a demand, Japanese Unexamined Patent Application Publication No. Heisei 9-208684 (Patent document 1) proposes to obtain a high fluidity polycarbonate resin for an optical recoding medium, which has less low-molecular-weight carbonate compound and less polycarbonate oligomer in the polycarbonate resin and which hardly generates matters that adhere to the stamper, by forming a reaction mixture by blowing phosgene into bisphenol, adding a quaternary ammonium salt to that reaction mixture to allow polymerization for a predetermined molecular weight, and then adding a molecular weight modifier (terminating agent).
Another example for producing a high quality polycarbonate resin is proposed in Japanese Unexamined Patent Application Publication No. Heisei 1-275629 (Patent document 2) in which two types of molecular weight modifiers, namely, terminating agents are used to produce a polycarbonate having improved balance between fluidity and impact resistance. In addition, Japanese Unexamined Patent Application Publication No. 2001-208917 (Patent document 3) proposes use of a polycarbonate having excellent fluidity and mechanical strength for a light guide plate.
Furthermore, Japanese Unexamined Patent Application Publication No. Heisei 8-325369 (Patent document 4) and Japanese Unexamined Patent Application Publication No. 2002-105190 (Patent document 5) disclose a method for reducing the amount of a low-molecular-weight carbonate compound having a molecular weight of 1,000 or less contained in a polycarbonate resin.